1. Field of the Invention
The present invention relates to a method and an apparatus for removing an image, which has been formed on a recording material using an image forming apparatus such as copiers, printers and facsimile machines, from the recording material. In addition, the present invention also relates to an image peeling member for peeling an image from a recording material.
2. Discussion of the Background
Recently, printers, analogue copiers, digital copiers and facsimile machines using electrophotography are broadly used, and a huge amount of paper is used therefor. Since paper is prepared using pulp, which is obtained from wood, use of such a huge amount of paper causes deforestation, resulting in deterioration of global environment. Therefore, it is a social issue to lower the consumption of paper. In addition, since there is a limit to waste disposal sites, it is also a social issue to reduce the amount of waste.
In attempting to resolve the issues, paper recycling methods in which disused information recording papers are collected and pulp prepared from the collected paper waste in paper factories is reused for new papers have been conventionally used. However, these paper recycling methods have drawbacks in that a large amount of energy is consumed for transporting the collected paper waste, preparing pulp using the waste paper and making new paper from the pulp; and the recycled paper has poor physical qualities such as low stiffness and whiteness, and produces images with poor image qualities such as formation of blurred images. In addition, when high quality information recording paper having high whiteness is prepared using recycled pulp, the manufacturing costs thereof are often higher than the costs of manufacturing such a high quality recording paper using a new raw materials. Further, when disused information recording paper is collected, there is a risk of occurrence of a problem in that information such as personal information written in the disused recording paper is disclosed to the public.
In attempting to solve the problem of the recycled paper, recording materials which can be reused by removing images therefrom and methods in which images formed on a recording material is removed to reuse the recording material have been proposed. For example, published unexamined Japanese patent application No. (hereinafter referred to as JP-A) 01-297294 discloses a technique in that an image formed on a recording material such as plastic films, metal foils, non-penetrative paper, and ceramics is heated while a thermofusible peeling member is overlaid on the image to be removed from the recording material. In addition, JP-A 04-64472 discloses a device which removes an image formed on a surface of a recording material by an electrophotographic method, which surface is treated with a release agent, by contacting a surface of an endless belt (serving as a peeling member), which surface includes a thermofusible resin, to the image to transfer the image from the recording material to the endless belt.
Although the means for removing images is described in these publications, means for treating the peeling member on which images are transferred is not described therein. Specifically, when images are accumulated on a peeling member, the heat capacity of the peeling member increases and the heat conductivity thereof deteriorates. Therefore, it is necessary to remove the images accumulated on the peeling member in order to repeatedly use the peeling member.
It is possible to remove images on a recording material using a peeling member having an outermost layer including a thermofusible or thermoplastic material. However, in this case the images are mixed with the thermofusible or thermoplastic material on the peeling member because both the images and the thermofusible or thermoplastic material have a fluidity, and therefore it is hard to separate the images from the thermofusible or thermoplastic material. Therefore, the above-mentioned image removing devices cannot be commercialized.
Images accumulated on a peeling member are not removed, not only cause increase in the heat capacity and deterioration of the heat conductivity of the peeling member, but also roughen the surface of the peeling member. When such a roughened peeling member is used, the surface of the peeling member cannot be contacted with the entire image to be removed from a recording material, thereby causing a problem in that a portion of the images remains on the recording material without being removed. Therefore, it is necessary to smooth the surface of the peeling member after every image removing operation. When the smoothing operation is performed on a peeling member, the thermofusible or thermoplastic material has to be heated to a relatively high temperature compared to the melting point or glass transition temperature of the thermofusible or thermoplastic material so that the material has a high fluidity. In this case, a large amount of energy is needed for performing this smoothing operation after every image removing operation. This also prevents the above-mentioned image removing devices from being commercialized.
In attempting to well remove images from recording materials, techniques in that removing operations are repeated several times have been proposed. For example, JP-A 07-56472 discloses a method and a device in which a liquid including water as a main component is coated on an image to destabilize the image by decreasing the adherence of the image to the recording material, and then two peeling members are repeatedly contacted with and separated from the destabilized image to remove the image from the recording material. The reason why the method uses two peeling members is as follows. When a solid image having a large area, on which the destabilizing liquid has been applied, is removed using one peeling member, peeling is not caused at the interface between the image and the recording material and is caused within the recording material. This is because the binding force among the cellulose fibers constituting the recording material decreases due to swelling of the fibers. Therefore, the method uses two peeling members, one of which is located on an upstream side relative to the feeding direction of the recoding material and which is configured to adhere to a part of the image to remove the part of the image from the recording material. The other peeling member, which is located on a downstream side, is configured to adhere to the entire surface of the solid image to remove the residue of the solid image.
It is described in JP-A 07-56472 that a resin which is the same as or similar to the resin including in the toner constituting the image to be removed is used for the surface of the peeling member and in addition the area of the image removing portions of the surface of the two peeling members, which portions have an image removing ability and can be contacted with the image to be removed is changed. However, it is not described therein to use both a peeling member having an thermoplastic surface and a peeling member having a non-thermoplastic surface. In addition, it is not described therein to use different cleaning members for removing the images transferred to the two peeling members.
Although (monochrome) images constituted of a toner having a relatively large particle diameter can be removed relatively well by this method, images constituted of a toner having a relatively small volume average particle diameter of not greater than 8 μm, multicolor toner images and half tone images cannot be well removed. For example, multicolor images typically include secondary or tertiary images (i.e., images such as two or three different color images are overlaid), which are relatively thick, and half tone images which are relatively thin. If a secondary or tertiary image is located adjacent to a half tone image, the half tone image is hardly contacted with such peeling members, and thereby the half tone image cannot be well removed. Particularly, a peeling member using a material, such as resins having a high glass transition temperature (Tg) and metals, which does not achieve a plasticity at the temperature to which the peeling member is heated to remove an image, cannot remove such a multi-color image or an image constituted of a toner having a relatively small particle diameter.
JP-A 09-212050 discloses a device in which an image removing operation is performed plural times to remove an image from a recording material using a thermal transfer method and then the toner particles scattered around the image (i.e., toner particles located on a background portion of the image near the image portion) are removed using electrostatic force. It is described therein that the toner particles on the background portion cannot be removed from the recording material by performing the thermal transfer peeling operation plural times. However, almost all the toner particles located on a background portion are also thermally fixed with a fixing device, and therefore such toner particles are hardly removed by such an electrostatic force as mentioned in JP-A 09-212050. Particularly, in a multi-color image the upper toner layers of a secondary or tertiary color image has to be transparent so that the color image has good color reproducibility, and therefore the upper toner layers are fully melted. Therefore, a color image is fixed on a recording material relatively strongly compared to a monochrome image. Therefore color toner particles on a background portion cannot be removed by such an electrostatic force.
JP-A 09-212050 points out that removal of toner particles scattered around images is only a problem to be solved. However, when a cycle of recording an image on a recording material and removing the image from the recording material to reuse the recording material is repeated many times, toner particles located on the entire background area (i.e., background fouling) have to be removed. All images formed on recording materials using electrophotographic image forming apparatuses have background fouling which is constituted of toner particles. When the above-mentioned cycle is performed several times, the toner particles remaining on a background portion without being removed are not so noticeable. However, when the cycle is performed a number of times, the toner particles are accumulated on the recording material, resulting in increase of the background density. Therefore, the resultant image formed on such a recording material is visually undesirable. When such an image is removed to reuse the recording material, a problem which occurs is that a negative image of the image portion is formed on the recording material because the toner particles under the image portion are removed but the toner particles on the background area remains on the recording material. This is also a problem in view of security.
In particular, the problem in that toner particles remain on background areas without being removed and the toner particles are accumulated on the recording material occurs if the toner particles have a volume average particle diameter of not greater than 8 μm and/or the toner particles are present on a background area near a multi-color image.
Further, JP-As 09-197926 and 10-274909 have disclosed image removing methods and apparatuses in which an operation cycle of performing attaching, pressing and detaching of a peeling member on a recording material is carried out plural times. The techniques described therein are similar to that of JP-A 07-56472 mentioned above although the purposes thereof are different from each other. Therefore, the techniques are not effective for removing images having secondary or tertiary color images and half tone images; and for removing toner particles (image forming materials) present on background areas.
Because of these reasons, a need exists for an image removing method by which images having secondary or tertiary color images and half tone images; and toner particles present on background areas can be well removed.